Hydraulic valve control for bilge discharge



Jan. 20, 1959 E. J- SVENSON 2,869,500

HYDRAULIC VALVE CONTROL FOR BILGE DISCHARGE Original Filed July 22, 19492 SheetsSheet 1 HIIH I KHHIhm .24 46- J4 J6 44 Z17 .5Ze/w0m Jan. 20,1959 E. J- SVENSON 2,869,500"

HYDRAULIC VALVE CONTROL FOR BILGE DISCHARGE Original Filed July 22, 19492 Sheets-Sheet 2 INVENTOR. flizes'z J firasaw HYDRAULIC VALVE QONTRGLFOR BILGE DIECHARGE Ernest J. Svenson, Rockford, ill.

Continuation of application Serial No. 166,197, July 22, ggllul'hlsapplication November 21, 19%, Serial No.

9 Claims. (Cl. 114- 133) This invention relates to valve controlmechanisms and more particularly to hydraulically operable mechanismstor Sfllfllfigremotely positioned valves. This is a contmuation of myctr-pending application Serial No. 106,197, filed July 22, 1949,now'abandoned.

There are many applications in which it is desirable to control theoperation of valves from a remote point, as for example, in chemicalplants where the conduits carrying fluids are relatively inaccessible orin hydraulic presses where it is desirable to control a number ofoperatrons from a common point. Control of the flow of water to and fromthe bilges of a ship is an application to which my invention is welladapted and has been chosen for purposes of illustration. In suchinstallations, the valves are frequently subject to corrosion or gummingso that they become stuck whereby a positive substantially uny1eldingforce means is required for insuring proper and safe operation of thevalve.

Often it is desirable to remove all or a part of the water from thebilges of a ship while at other times it is desirable to pump water intothe bilges as for ballast purposes. Generally, the bilges are located atthe bottom of a ship and are relatively inaccessible. if it werenecessary to operate the valves at their various locations, 21 greatamount of effort would be entailed in going from one to the other, andan intolerable time lag would be encountered between the time it wasfirst wished to actuate the valve and the time the valve was actuated.

In the past remote control of valves has been attempted by the use ofreach rods. To enable a number of valves at different locations to beoperated from a central control point the reach rods have often beenflexible shafts. In the type of ship chosen for example, the controlroom is generally located 50 feet or more above the valve position inthe bilge, and is furthermore displaced laterally a distance on theorder of 30 feet. When it is considered that the various bilges in aship may be located 75 feet apart, it may be readily seen that extremelylong each rods were required, often making bends of up to 90 degrees. Itis apparent that the friction between these flexible reach rods andtheir supports was very great, and there was an enormous loss of power.The sea Water which passes to and from the bilges through the variousvalves is quite corrosive, and in addition tends to deposit sticky orgummy substances on the valve, and as a result the valves frequentlystick. Due to the enormous power loss in flexible reach rods it hasoften been com-.

pletely impossible to open sticky valves from a remote location by suchmeans.

Remote control of valves has been attempted with compressed air but hasbeen unsatisfactory as it provides a yieldable or compressible force andhas often been unable to open sticky valves. Another disadvantage ofcompressed air is that, in the event a sticky valve is encountered, alarge volume of air must be delivered to raise the pressure within thesystem sufiiciently to start the valve after which the resistance orload provided by the valve may drop considerably so that the expandingair in the system may shiftthe valve at high speed and thus createinertia forces which will cause injury to the valve structure.Furthermore, it is imperative that the position of the valve be known inthe control room and indication is unreliable with an air medium. If avalve control was in an open position in the control room, it was noassurance that the valve itself would be open because if it were stuckthe air would merely compress enough to compensate for the dilference inthe control position.

Among the important objects of this invention is the provision of ameans for solving the problems noted above, namely, the provision ofpositive substantially unyielding force means for actuating valves froma remote location without unnecessary loss of power and the provision ofa positive indication of the valve position.

A more specific object of the present invention is to provide novelhydraulic means for meeting the above named objectives.

It has been contemplated that it would be possible to provide ahydraulic line from a control line directly to an actuating mechanismassociated with each valve. The size of each such hydraulic line wouldnecessarily vary with the size of the valve and it is apparent that thiswould entail a large number of hydraulic lines of different sizes, allrelatively large.

it is accordingly an object of the present invention to provide valvecontrol means operable from a distant point,

each of such means being connected to the remote point by a smallhydraulic line of standard size.

A further object of this invention is to provide a hydraulic remotelyoperable valve control means requiring a minimum of hydraulic fluid.

A more specific object this invention is to accomplish this last namedobject by means of a differential piston, the fluid being forced out ofone end of the piston returnin to the hydraulic system connected to theother end of said piston.

An important object o-f this invention is to provide means for actuatinga valve at the location of the valve as well as from a remote location.

A further object of the present invention is to provide a novelhydraulic system for actuating a valve of the type contemplated herein,which hydraulic system is con structed so as to provide an indication ofthe position of the valve both at a location adjacent the valve and ata.

location remote from the valve.

Other and further objects and advantages of the present invention willbe apparent to those skilled in the art from the following descriptionwhen taken in conjunction with the accompanying drawings in which:

Fig. l is a fragmentary cross sectional, somewhat schematic view takenthrough a ship embodying my present invention;

Fig. 2 is a fragmentary longitudinal sectional view of a portion of theship shown in Fig. 1;

Fig. 3 is a flow diagram embodying the invention;

Fig. 4- is a side view mostly in section showing a valve and itsassociated actuating mechanism;

Fig. 5 is-a top plan view showing the mechanism for operating the valveat the location of valve; and

Fig. 6 is a fragmentary sectional view showing the valve and actuatingmechanism in a difierent position from that shown in Pig. 4.

In Figs. 1 and 3 is shown somewhat schematically an installation of thepresent invention in a ship. The ship may have one or more decks ill. Atthe upper part of the ship are the various bridges and control roomswherein a valve control panel to be described later may be located. Abilge 14 at the bottom of the ship, which is preferably compartmentedinthe usual way, has been chosen for illustration, although it is to beappreciated that Water or other fluids maybe located in othercompartments at various locations and elevations throughout the ship;for example, water stored for fire fighting purposes, and my valveactuators would be installed at all such locations. Pipe lines 16 maylead from a group of bilge compartments or in a small ship from all ofthe bilge compartments to a manifold 18 having valves 20 and aninlet-outlet pipe 22 leading to a pump 23. When it is desired to emptyone or more of the bilge compartments the valves 20 corresponding tothese compartments are opened and the pump is actuated so as to drawwater through the lines 16 to the manifold 18 and out through the pipe22 to be pumped out of the ship. If it is desired to pump water into thebilges the pump may be actuated to pump water through the pipe 22 intothe manifold 18. With a ship of considerable size there will generallybe several manifolds as shown in Fig. 2 so that pipe lines from thebilge compartments to the manifold need not be overly long and themanifolds need not be of excessive size.

The hydraulic system utilized in this invention is best seen in Figs. 3and 4. A reservoir 24 contains hydraulic fluid 26 which is pumpedthrough an intake strainer 28 by means of a pair of low capacity highpressure pumps 30, which are preferably gear pumps, to an accumulator32. One of the pumps is operated continuously to maintain hydraulicpressure and both may be actuated if necessary to maintain hydraulicpressure when a number of valves are opened. It is to be appreciatedthat the foregoing parts may be provided in duplicate for standbyservice or to provide more fluid and higher pressures when an unusuallylarge demand is made on the system. The accumulator 32 has a by-passvalve which may be set at any desirable pressure, as for instance from200 to 600 pounds per square inch, to pass fluid through a drain line 34leading to the reservoir 24. From the accumulator a fluid power line 36leads to a junction point from which a fluid power line 38 leads to acontrol panel 40 in a valve control room as previously mentioned. On thecontrol panel are situated any suitable number of control valves 42, 44,46 and 48 having actuating handles 50, 52, 54 and 56 respectively.Although but four control valves are shown in Fig. 3 it is apparent thatany number of such valves may be utilized, there being one to correspondwith each bilge valve. When any of the valve handles 56 is in theleftmost position shown in solid lines in Fig. 3 the control valve ofwhich that handle is a part is in open position, whereas when it is inits furthermost position to the right the valve is closed. Toaccommodate hydraulic fluid lost by leakage and by actuation of thesevalves a drain line 57 is provided from the valves 42-48 leading to thedrain line 34 and hence to the reservoir 24.

From the junction point of the power lines 36 and 33 another hydraulicpower lines 58 leads downward toward the bilge 14 and splits off tovalve actuators 60, 62, 64 and 66 associated with the various valves 20,all of these valve actuators, of which there is any desirable number,being connected in parallel to the hydraulic power line. Between each ofthe valve controls 42-48 and valve actuators -66 is a pilot line 68, 70,72 and 74 shown in incomplete dotted lines in Fig. 3. Each of thesepilot lines is utilized to actuate a pilot valve as will be explainedsubsequently and as little force or 'fluid is used to actuate the pilotvalve, the pilot lines 63-74 may be of small diameter.

As each of the valve actuators is the same except for size, only theactuator 60 will be described, it being understood that this descriptionapplies to all of the actuators. In Fig. 4 one of the valves 20 is shownin place in the manifold 18 with one of the pipe lines 16 threaded intoan aperture in the manifold and opening into the bottom of the valve. Acup-shaped member 76 having an axial aperture 78 is threaded into anaperture 80 in the manifold in line with the bilge pipe 16. The member76 is provided near its upper periphery with a valve seat 82 and anaxially shiftable cooperable valve member 84 fits on this seat when thevalve is in closed position. A reciprocable valve stem 86 having aflange 88 at its lower end is secured to the valve member 84 by means ofa nutlike member 90 having an enlarged portion 92 at the lower end of anaxial bore 94.

The upper part 96 of the valve 20 of the actuator 60 is secured to thetop of the manifold in any suitable manner with a depending portion 98fitting within an aperture 100 in the top of the manifold and co-axialwith the bilge pipe 16. The part 96 has an aperture 102 in its dependingportion of substantially the same diameter as the valve stem 86. Theaperture 102 is enlarged to form an aperture 104 of large diameter, partof this aperture being in an upstanding portion 106 of the valve part96. in the aperture 104 and surrounding the valve stem 86 may be placedpacking 108 to prevent axial leakage along the valve stem and thepacking may be secured in place by a bushing 110 extending downward intothe aperture 104. The bushing may be held in place by any suitablemeans, such as bolts 112 passing through a flange 114 at the upperportion of the bushing 110 and threaded into the upper part 96 of thevalve.

An actuator support 116 which is secured in any desirable fashion atopthe upper part 96 of the valve carries the actuator 60 at its upperextremity and secured thereto in any desirable fashion. The hydraulicactuator 60 includes a cylindrical casing 118 having an axial bore orcylinder 120 of relatively large diameter in its lower portioncommunicating directly with a co-axial cylinder 122 of smaller diameterat the upper end of the casing 118. A relatively small piston 144 fitswithin the cylinder 122 and is secured by a rod or shaft 146 to a largerpiston 143 fitting within the lower cylinder 120. A piston rod 150extends downwardly through a small aperture 152 and a larger aperture154 in an upstanding central portion 156 of the actuator support and hsaits lower extremity adjacent the upper extremity of the valve stem 86 towhich it is rigidly secured by a coupling 158 in any desirable mannerincluding threadedly engaging the piston rod 150 and valve stem 86.Leakage between the upstanding portion 156 of the actuator support andthe casing 118 is prevented by a sealing ring 160 or the like placedtherebetween. Axial leakage along the piston rod 150 is precluded bypacking 162 secured within the aperture 154 by means such as a nut 164threaded into a slightly enlarged portion of the aperture 154. Adjacentthe lower end of the cylinder 120 an inlet-outlet line 166 leads to apressure sensitive pilot mechanism 168, a sealing ring 169 preventingradial leakage between the pilot mechanism 163 and the casing 118. Thetop of the upper-cylinder 122 and hence the upper face of the piston 144are preferably open to the hydraulic power line 58 to normally urge thevalve actuator downward, but it is contemplated that the downward forcecould be supplied by a coil spring located in the cylinder 122. It is tobe noted that the differential piston is arranged so that hydraulicpressure applied to the large end creates a relatively great force forshifting the valve 84 from the valve seat even in the event the valvemember 84 is stuck. Furthermore, when the pressure against the largepiston end is relieved, the relatively small force created by thepressure against the smaller end of the dilferential piston assemblyserves to move or hold the valve 84 against the valve seat effectivelybut without substantial danger of injury to the valve and valve seat.

The pilot mechanism 168 comprises a body portion 170 having an axialbore 172 therethrough, the bore being of different diameters atdifferent points, as may readily be seen in Figs. 4 and 6. The powerline 58 enters the body portion 170 from the side and the hydraulicfluid in the line has access through a transverse bore 174 to the bore172. A lower drain line 176 communicates by means of a transverse bore178 with another portion of the bore 172. Upper and lower pilot pistons179 and 180 fit withen es U in the aperture 172, the lower of thesepistons having its lower face in communication with the hydraulic fluidin the pilot line as which is threaded into or otherwise secured to abottom portion 182 secured in any suitable fashion to the body member171'), an axial ring 184 of suitable construction preventing radialleakage between the members 182 and 1711. A piston rod 186 separates thepilot pistons 179 and 1% and may be formed integral therewith. A pistonrod 183 of relatively large diameter extends upwardly from the piston179 and is formed integral with a control rod 196* of reduced diameterwhich extends upwardthrough a cap 192. The cap 192 is secured to thebody 1719 in any desirable manner with a sealing ring 194 interposedtherebetween to prevent axial leakage. A coil spring 193 is placedwithin the aperture 172 abutting against the cap 192 and piston 179 soas to normally force the latter downward. It is to be noted that thepiston 17?, when in the position shown in Fig. 4 is disposed so that itsperipheral surface blocks the power inlet bore 174 so that the pressureof hydraulic fiuid in the bore 174 does not substantially restrainshifting of the pilot pistons. .Thus, the force required to raise thepilot pistons need only be suificient to overcome the spring 193. Adrain line 195 is provided running from the tops of cylinders 121i and172 to a point in the cylinder or bore 172 adjacent the drain line 176so that any fluid leaking into these spaces past the various cylinderscannot prevent upward movement of the cylinders. As shown in Figs. 4 and6, the lower end of the drain line 195 communicates with an annularenlargement of the bore 172, and the drain line 176 also communicateswith this annular enlargement. Thus communication is always establishedbetween the drain lines 176 and 195, regardless of the position of thepilot piston 180. An upper extension of the cap 192 is bifurcated toform a pair of arms 1% and 198. A manual control handle 2% having a knobam at one end is located between the arms 1% and 198 and is pivotally'secured thereto by means of a pivot pin 204 passing through both armsand the handle. A lockingmechanism 206 is located in the arm 1% andcomprises a pin 2118 receivable in an aperture in the handle 209. Thepin 208 has a collar 210 spaced from its extremity and a coil spring 214is compressed between the collar 210 and a nut-like member 216 threadedinto the aperture 212 to bias the pin 208 toward the handle 200 at alltimes. A handle 218 is provided to retract the pin 208 against theaction of the spring 214 so that the handle 200 may be moved if desired.An elongated vertical aperture 220 is provided in the handle 2% toaccept the control rod 190 which has a transverse pin 222 cooperablewith a scalloped portion 224 of the top surface of the handle 2%. Due

to the particular connection between the control rod 194 and the handle2% it is possible for the control rod to rise without disturbing theposition of the handle and it is also possible for the control rod to beraised by the handle.

If it is desired to operate the valve 20 from a distant point the handle50 of the control 42 is moved to the open position. This appliespressure from the hydraulic power line 38 to the pilot line 63 andraises the pilot pistons 180 and 179 to the position shown in Fig. 6,upward movement of these pistons being stopped by abutment of theshoulder between the piston rod 188 and control rod 190 against the cap1%. The drain 176 is sealed from the power line 53 and the line 166 bythe piston 18% and the power line 58 communicates through the bore orcylinder 172 to the line 166 and to the lower part of the cylinder 120.At the same time, the drain 176 remains in communication with the drainline 195. The pressure from the hydraulic power line '8 against theupper face of the piston 144 has prior to this time kept the valve in aclosed position but as the area of the lower face of the piston 1.48 isgreater than the area of the upper face of tie piston 144, a largerforce is developed than the force urging the piston 14 d downward andthe two pistons and piston rod move upward to the osition shown in Fig.6 to lift the valve stem 86 andppen the valve 20 without thenec'essity'of having a valve associated with the upper piston 144. Thetop of the piston 144 acts as a stop so that the piston 148 doesnot'move upward far enough to close off the drain line 195 but insteadleaves some clearance. It is apparent that the relative sizes of thepistons 14 and 148 will be governed by the size of the valve to beopened and the degree of stickiness liable to be encountered. It is tobe noted that the volume of hydraulic fluid filling the cylinder 120need not be moved in its entirety from the accumulator 32 as a sizableportion of it is pumped from the cylinder 122 into the hydraulic powerline 58 by the upward movement of the piston 144. When it is desired toagain close the valve, the handle 50 of the control 42 is moved toclosed position and hydraulic pressure is no longer applied to the pilotline 68. The spring 1% then forces the pilot pistons 179 and downward tothe position shown in Fig. 4, sealing otf the power line and opening thelower portion of the cylinder 120 to the lower drain 176. It is to benoted that when the pilot pistons are in the raised position thehydraulic fiuid'between the adjacent or inner ends of the pilot pistonsacts against these ends in opposite directions with substantially equalforce. As a result the pressure in the power line in no way acts to urgethe pilot piston assembly in either direction or to hold the pilotpiston assembly in the upper position so that the spring may easilyshift the pilot piston assembly downwardly when the pressure in the line68 is relieved. As pressure is no longer applied against the lower faceof the piston 148, the pressure from the direct power line 58 on theupper face of the piston 144 pushes the pistons, the piston rod 151),the valve stem 36 and the valve member '84 downward to'close the valve.The fluid in the lower part of the cylinder 120 is forced out throughthe line 166, the cylinder 172 and lower drain 176 and returned to thereservoir 24.

The valve may also be actuated directly at the manitold by pushing downon the knob 202 of the handle 200 after retracting the pin 21l8'by meansof the handle 218 to lift the control rod 19!) and move the pilotpistons to the same position which they occupy when forced upwards bypressure from the pilot line 68. It is apparent that l have hereinprovided a means for operating a valve from a distant point or from anear point. The operation is simple and sure. A minimum of transmissionloss is engendered, and a positive indication of the valve positionappears at the control point. It is further apparent that through theuse of a single hydraulic power supply line from the valve control lineto the vicinity of the bilge and of a differential piston in pumping avolume of fluid back into the power supply line a minimum of hydraulicfluid is required.

Although 1 have shown and described a particular embodiment of myinvention, it is apparent that my invention has utility in otherinstallations such as chemical plants and oil fields and that changesmay be made in the form, construction and arrangement of the partswithout departing from the spirit of the invention or sacrificing any ofits attendant advantages and the right is hereby reserved to make allsuch changes as fairly fall within the scope of the appended claims.

The invention is claimed as follows:

1. In a ship, a plurality of relatively inaccessible bilge compartments,a manifold, means for maintaining a predetermined pressure in saidmanifold, means including a plurality of valves each interconnecting oneof said bilge compartments and said manifold to control the egress andingress of water from and to said bilge compartments, a plurality ofvalve actuators mounted on said manifold and each mechanically linked toone of said valves, each of said valve actuators being operable byhydraulic fluid under pressure, a source of hydraulic fluid, means forapplying pressure to said hydraulic fiuid,

means including valve means connecting each of said actuators to saidpressure applying means, a plurality of remote control means connectedto said pressure applying means and each including a valve remote fromsaid valve actuators and pressure sensitive means adjacent each valveactuator for operating said valve actuators and a hydraulic line linkingeach of said pressure sensitive means and one of said remote controlvalves for selectively applying pressure to said pressure sensitivemeans whereby to operate said valve actuators from a remote location insaid ship.

2. In a ship, a plurality of relatively inaccessible bilge compartments,a manifold in said ship adjacent said bilge compartments, means formaintaining a predetermined pressure in said manifold, meansinterconnecting said bilge compartments and said manifold including aplurality of valves on said manifold and each controlling the egress andingress of water from and to one of said bilge compartments, a pluralityof valve actuators mounted on said manifold and each mechanically linkedto one of said valves, each of said valve actuators including adifferential piston having a larger diameter end and a small diameterend and operable by hydraulic fluid under pressure, a source ofhydraulic fluid, relatively low capacity high pressure pump remotelydisposed relative to said valve actuators for supplying hydraulic fluidunder pressure thereto, a relatively large diameter hydraulic power lineinterconnecting said pump and each of said valve actuators, said powerlines at all times being in open communication with the small end ofeach of said differential pistons, a plurality of hydraulically operablepilot means each associated with and disposed adjacent to one of saidvalve actuators, a drain line from each of said pilot means to saidsource to return hydraulic fluid to said source, means in each of saidpilot means selectively interconnecting the large end of saiddifferential piston with said hydraulic power line adjacent said smallend of the differential piston and said drain line, the ends of each ofsaid differential pistons thereby being in open communication with oneanother when said power line is interconnected with the large end ofthat piston so that fluid expelled by the small end augments fluid insaid power line passing to the large end, remote control means, and meanlinking said remote control means to the interconnecting means of eachof said pilot means for operating said pilot means selectively toactuate said valves from a distant location.

3. In a system for controlling fluid flow including a valve seat and avalve member shiftable toward and away from said seat and susceptible tosticking against said seat, a differential actuator piston havingopposite relatively large and small diameter ends and ri idly connectedto said valve member for positively shifting said valve member away fromsaid valve seat when hydraulic liquid under pressure i applied to saidlarge piston end and for positively moving said valve member toward andagainst said valve seat when hydraulic liquid under pressure is appliedonly to said small piston end, remotely positioned high pressure andrelatively low capacity means for supplying hydraulic liquid underpressure from a liouid reservoir, power conduit means connected withsaid liquid su ply means and continuously in open communication withsaid small piston end, an actuator control valve body adjacent saidpiston and communicating with said large piston end and with said powerconduit substantially at said small piston end, a drain line extendingfrom said control valve body to said reservoir, piston valve meansaxially sildable in said control valve body and including a pair ofconnected axially arranged portions respectively having their sidesblocking communication between said power conduit and said large pistonend when in one position and blocking communication between said largepiston end and said drain line when in a second position, said pistonvalve means prosaid power conduit and said large piston end when saidpiston valve means is in said second position so that the hydraulicfluid under pressure from the power conduit is ineffective for shiftingthe said piston valve means, spring means normally biasing said pistonvalve means toward one of said positions, a remotely positioned controlvalve connected with said liquid supply means, and a hydraulic linebetween said remotely positioned control valve and said actuator controlvalve body for directing hydraulic liquid under pressure to shift saidpiston valve means to the other of said positions.

4. A system, as defined in claim 3, wherein valve portions are disposedwith a space therebetween, which space provides said passageway forconnecting said power conduit and said large piston end when said pistonvalve portions are in said second position and also provides forcommunication between said large piston end and said drain line whereinsaid piston valve portions are in said first position, opposing ends ofsaid piston valve portions having substantially equal areas so thathydraulic liquid flowing through said space is ineffective to shift saidpiston valve assembly.

5. A system, as defined in claim 3, which includes mechanical meanssubstantially at said control valve body and connected with said pistonvalve means and operable for shifting said piston valve means againstthe action of said biasing means from said one position to the other ofsaid positions.

6. A system, as defined in claim 5, wherein said remotely locatedcontrol valve means is a two-position valve and includes an actuatinglever which by its position provides an indication of the position ofsaid differential piston.

7. A system, as defined in claim 5, wherein said mechanical meansincludes an actuating lever which by its position provides an indicationof the position of said differential piston.

8. In a system for controlling fluid flow including a valve seat and avalve member shiftable toward and away from said seat and susceptible tosticking against said seat, a differential actuator piston havingopposite relatively large and small diameter ends and rigidlyconnectable to said valvemember for selectively positively shifting saidvalve member away from said valve seat and for positively moving saidvalve member toward and against said valve seat, remotely positionedhigh pressure and relatively low capacity means for supplying hydraulicliquid under pressure from a liquid reservoir, power conduit meansconnected with said liquid supply means and continuously in opencommunication with said small piston end, an actuator control valve bodyadjacent said piston and having a bore therein, said control valve bodyincluding passageways respectively communicating with said large pistonend and with said power conduit adjacent said small piston end and withaxially spaced side portions of said bore, a drain line extending fromanother side portion of said bore to said reservoir, piston valve meansaxially slidable in said bore and including a pair of axially arrangedconnected pistons with a space therebetween respectively having theirsides blocking communication between said power conduit and said largepiston end passageway when in one position and blocking communicationbetween said large piston end passageway and said drain line when in asecond position, the space between said pistons providing a passagewayfor connecting said power conduit and said large piston end passagewayswhen said piston valve assembly is in said second position, spring meansnormally biasing said piston valve means toward one of said positions,mechanical means at said valve body and connected with said piston valvemeans for shifting said piston valve means toward the other of saidpositions, a remotely positioned control valve connected with saidliquid supply means, and a hydraulic line between said remotelypositioned control valve and said actuator control valve body fordirecting hydraulic liquid under pressure to shift said piston valvemeans to said other of said positions.

9. In a system for controlling fluid flow including a valve seat and avalve member shiftable toward and away from said seat and susceptible tosticking against said seat, a differential actuator piston havingopposite relatively large and small diameter ends and rigidlyconnectable to said valve member for selectively positively shiftingsaid valve member in one direction when hydraulic liquid under pressureis applied to said large piston end and for positively moving said valvemember in the opposite direction when hydraulic liquid under pressure isapplied only to said small piston end, remotely positioned high pressureand relatively low capacity means for supplying hydraulic liquid underpressure from a liquid reservoir, power conduit means connected withsaid liquid supply means and continuously in open communication withsaid small piston end, an actuator control valve body adjacent saidpiston and communicating with said large piston end and with said powerconduit substantially at said small piston end, a drain line extendingfrom said control valve body to said reservoir, piston valve means insaid control valve body and including a pair of axially arrangedportions respectively having their sides for blocking communicationbetween said power conduit and said large piston end when in oneposition and blocking communication a passageway through a said portionthereof for connecting said power conduit and said large piston and whensaid piston valve assembly is in said second position in a manner sothat hydraulic fluid under pressure from said power conduit isineffective for shifting the piston valve means, spring means normallybiasing said piston valve means toward one of said positions, mechanicalmeans at said valve body and connected with piston valve means forshifting said piston valve means toward the other of said positions, aremotely positioned control valve connected with said liquid supplymeans, and a hydraulic line between said remotely positioned controlvalve and said actuator control valve body for directing hydraulicliquid under pressure to shift said piston valve means to said other ofsaid positions.

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